The present invention relates generally to electrical switch enclosures, and more specifically to an actuator mechanism for such an enclosure that automatically locates and prepositions an externally viewed handle upon closing the enclosure cover to reflect the true operational state of the switch contained therein.
Switches for use in electrical circuits associated with machinery and other equipment are well known in the art. Used alone or in a group, they control the flow of electrical current. As disclosed by U.S. Pat. No. 3,284,731 issued to Nicol, they may take the form of a toggle switch with a lever that is manually operated between "on" and "off" positions to energize or deenergize the switch, thereby completing or interrupting the electrical circuit. They may likewise comprise a circuit breaker switch having a tripping mechanism that automatically interrupts the electrical circuit in response to an infrequent, abnormal condition like an overly high voltage, as taught by U.S. Pat. No. 2,560,628 issued to Brown, and U.S. Pat. No. 3,771,081 issued to Strobel.
Such switches are frequently placed in protective housings when used in explosive atmospheres or otherwise harsh environments. These housings are commonly cast from aluminum with one-half-inch-thick walls to prevent or contain explosions, moisture penetration, etc. A mating cover permits access to the switch mechanism contained therein. These switches normally feature a handle on the exterior of the enclosure that is operatively connected to the switch toggle lever contained inside the enclosure in order to permit operation of the switch without the need to remove the enclosure cover. In the case of explosion-proof or hazardous location-rated enclosures, such an externally operated switch may be a necessity.
U.S. Pat. No. 3,264,443 issued to Farina et al., U.S. Pat. No. 3,287,514 issued to Bachman, and U.S. Pat. No. 3,422,238 issued to Rys et al. disclose designs for such an externally mounted handle that is operatively connected to the toggle switch inside the enclosure by an actuator rod. In the case of Farina, the handle and rod are simply moved toward or away from the enclosure side wall to move the toggle switch between the "on" and "off" positions. Bachman and Rys, by contrast, teach a structure by which rotational movement of the externally mounted handle is translated by an actuator mechanism into rectilinear movement of the toggle switch between the "on" and "off" positions. In both Farina and Bachman, however, the handle is mounted to the side of the enclosure, and the actuator mechanism is permanently connected to the toggle switch. Such a design, though, would be impossible for a cover-mounted handle in which the actuator mechanism must be readily detachable from the toggle switch in order to permit opening of the cover to provide access to the switch.
It is also known in the trade to provide an externally mounted handle on the cover of the enclosure. In U.S. Pat. No. 1,989,393 issued to Anderson, for example, a rectilinearly biased external handle engages the toggle switch mounted inside the enclosure, and moves in parallel therewith. U.S. Pat. No. 2,180,501 issued to Blood discloses a handle that is detachably connected to the toggle switch by means of a clip, and slid in a direction parallel with the operational direction of the toggle switch. U.S. Pat. No. 2,610,272 issued to Platz, by contrast, uses a rotary-mounted handle connected to an actuator mechanism that raises or lowers a movable contactor in a direction normal to the handle, thereby completing and interrupting the electrical circuit. U.S. Pat. No. 1,924,351 issued to Doddridge, U.S. Pat. No. 2,752,464 issued to Seeger, U.S. Pat. No. 4,612,424 issued to Clark et al., and U.S. Pat. Nos. 3,742,401 and 3,771,081 issued to Strobel use handles connected directly or indirectly to a clip or other mechanism that translates the resulting rotary motion of the handle into rectilinearly biased movement that operates the toggle switch. The EWP Panel Board sold by Appleton Electric Company, the assignee of the present invention, uses a similar mechanical principal. Upon reattaching the cover to the enclosure of such devices, however, the externally mounted handle will not necessarily reunite with the toggle switch without cumbersome and difficult operator alignment. Moreover, the handle position may be out of phase with the operational state of the toggle switch, thereby indicating that the switch is "off" when, in fact, it is energized, and creating a safety hazard to an unaware operator. The two parts may not become realigned once again until the handle is rotated successively over time to the "off" and "on" positions.